Ok I'm to this forum, so bear with me, I have a 91 LTZ and have made a few minor changes to it. What are the capabilities of the computer in this car??? if any and can it be updated. I replaced my 195 thermostat with a 180 the car is running cooler but :banghead: my mileage dropped so either I change it back suffer $$$$ Help

In most cases, a hotter running engine is more efficient. When i say hot i mean 195-205 area. I also own a 91 LTZ, and i've yet to find anything other than performance chips. The ECM can be re-programmed with the right tools, but it would hardly be worth it. I don't know about you, but my old retired State Police car will haul the mail!!